Circular knitted tubular structure, and manufacturing method and manufacturing device of the same

ABSTRACT

A circular knitted tubular structure manufactured at low cost with use of a circular knitting machine is highly adaptable to bending due to flexibility, having tube inner and outer surfaces so soft that no abnormal noise is produced, and hence useful as a sleeve covering and thereby protecting a cable, such as an electrical wire and an optical fiber cable. The circular knitted tubular structure is formed of a fabric tape formed of circular knitted fabric having front yarn forming loops and back yarn having a higher heat shrinkage ratio than the front yarn and formed into a scrolled shape by letting the back yarn undergo heat shrinkage to have an overlap portion circumferentially overlapping 1.3 to 2.5 times. Apparatus for manufacturing the circular knitted tubular structure includes a furnace and a shape-forming jig.

TECHNICAL FIELD

The present invention relates to a tubular structure formed of circular knitted fabric and a manufacturing method thereof, and more particularly, to a circular knitted tubular structure suitable to a sleeve covering and thereby protecting a cable, such as an electrical wire and an optical fiber cable, installed to a vehicle that vibrates when driven, such as an automobile, and to a manufacturing method and a manufacturing device thereof.

BACKGROUND ART

Patent Literature 1 describes a corrugated tube having a cut in a length direction and an opening formed to open and close in a circumferential direction, which is adopted in the related art as the protecting sleeve described above. Besides a corrugated tube, a protecting sleeve formed of braid, warp knit, and weft knit is used. A protecting sleeve formed of knitted fabric as described in Patent Literature 2 specified below is also used. Further, an acoustic absorption protecting sleeve formed of woven fabric as described in Patent Literature 3 is proposed.

CITATION LIST Patent Literatures

Patent Literature 1: JP-A-2015-37333

Patent Literature 2: JP-A-2003-278058

Patent Literature 3: JP-T-2003-506579

-   (the term “JP-T” as used herein means a published Japanese     translation of a PCT patent application)

SUMMARY OF INVENTION Technical Problem

The corrugated tube described in Patent Literature 1 specified above has stretching properties and flexibility to some extent due to its corrugated shape. However, because the corrugated tube is made of hard synthetic resin to maintain durability, the corrugate tube fails to achieve sufficient stretching properties and flexibility in actual use. Moreover, when used in a vibrating object like an automobile, a cable stored in the corrugated tube and an inner surface of the corrugate tube hit against each other, in which case not only an abnormal noise, such as a chattering noise, is produced, but also the cable may possibly be damaged. A drawback of the corrugated tube is a need to overcome such an inconvenience by covering the cable with soft fabric or the like in advance or by bonding a shock absorber to the inner surface of the corrugated tube before the cable is stored in the corrugated tube. In addition, because the corrugate tube is hard, an abnormal noise may possibly be produced when the corrugated tube hits against a nearby object.

A wiring cord cover described in Patent Literature 2 specified above directly uses a tubular body. A diameter of cylindrically knitted fabric is determined by a cylinder diameter of a knitting machine. Hence, while cylindrically knitted fabric of a same diameter can be manufactured continuously, a cylinder needs to be replaced with another cylinder having a different diameter to manufacture cylindrically knitted fabric of various types each having a different diameter. Accordingly, as many knitting machines and cylinders as the number of different diameters are required. The wiring cord cover therefore has a drawback that facility costs are required and hence manufacturing costs are increased. In addition, because the cover has openings only at both ends of the cylindrically knitted fabric, a wiring cord cannot be covered with the cover after the wiring cord is connected to a device.

The acoustic absorption protecting sleeve described in Patent Literature 3 specified above is formed of woven fabric. The sleeve is therefore thin and lacks pliability and stretching properties. Hence, when the sleeve is curved, the sleeve fails to curve smoothly and bends instead, which raises a problem that a wiring stored inside is locally pressed hard. While a purpose of the sleeve is to reduce acoustic vibrations, the sleeve formed of thin, unpliable woven fabric exerts only limited vibration absorbing performance. In addition, woven fabric having an extremely fine width needs to be manufactured to form the sleeve. Hence, the acoustic absorption sleeve has a drawback in productivity. This drawback may be eliminated by using a fabric tape cut narrow from wide woven fabric prepared in advance. However, this countermeasure cannot be adopted because a warp of woven fabric readily frays and when heat cutting is applied to prevent fray, a melted cut portion becomes so hard that an electrical wire filled inside or a material making contact from outside is readily damaged.

The present invention was devised in view of the current situation of the related art and has an object to provide a circular knitted tubular structure manufactured at low costs, highly adaptable to bending due to pliability, having tube inner and outer surfaces so soft that no abnormal noise is produced, and hence useful as a sleeve covering and thereby protecting a cable, such as an electrical wire and an optical fiber cable, and a manufacturing method and a manufacturing device thereof.

Solution to Problem

Inventors of the present invention conducted an assiduous study and succeeded in providing an excellent tubular structure of the present invention by making improvements, regarding the circular knitted fabric, in points a, b, and c as follows.

a. Providing a tube with an end face which prevents the tube from fraying when a wiring is stored from a tube side surface and eliminates a concern about snagging or the like.

b. Providing a knitted fabric construction to shape a fabric tape cut from knitted fabric into an even and neat tubular structure and a shape-forming method.

c. Providing a knitted fabric construction to confer a shape retaining property and an elastic bouncing property to a tubular body.

More specifically, regarding the point a, the inventors paid attention to the fact that circular knitted fabric hardly frays when cut in a course (length) direction because all strands of yarn forming the circular knitted fabric is knitted in a wale (width) direction while only loops are chained in the course direction and no yarn is passed linearly in the course direction (longitudinal direction). The inventors discovered that a sleeve with a fray-proof side edge can be formed from a tubular structure by cutting circular knitted fabric in the course direction with an edged tool or the like after a width is adjusted to a circumference of a desirable tubular structure and using a cut surface left as is as the side edge of the sleeve.

Regarding the point b, the inventors discovered that a tubular structure having a neat cylindrical appearance is formed from a fabric tape cut from knitted fabric in the course direction by using different types of yarn each having a different heat shrinkable property on right and wrong sides of knitted fabric (corresponding to inside and outside of a tubular structure) and letting the yarn on the wrong side shrink more than does the yarn on the right side.

Regarding the point c, the inventors discovered that even when large size yarn is cut left as is after the large size yarn is passed appropriately on an inner side of a tube to maintain a neat tubular structure at normal times and also to confer restorability against an impact or hard pressing from the outside, a cut part of the large size yarn does not appear on the right side of the knitted fabric and hence damage on a contact portion on the outside and snagging can be prevented. The inventors achieved the present invention from the discoveries as above.

That is, a circular knitted tubular structure according to claim 1 of the present invention is formed of a circular knitted fabric tape having a length direction as a course direction and characterized in that the circular knitted fabric tape has a cut edge in the length direction cut and left as is and is formed into a scrolled tubular shape to have an overlap portion in a width direction.

A circular knitted tubular structure according to claim 2 of the present invention has the construction of the circular knitted tubular structure set forth in claim 1 and is further characterized in that the circular knitted fabric tape is formed of circular knitted fabric using yarn forming a right side and high shrinkage yarn passed on a wrong side and having a higher heat shrinkable property than the yarn, and that the overlap portion of the circular knitted fabric tape circumferentially overlaps 1.3 to 2.5 times in a scrolled shape. The yarn forming the right side referred to herein is not limited to yarn forming loops and may also include yarn exposed to the right side.

A circular knitted tubular structure according to claim 3 of the present invention has the construction of the circular knitted tubular structure set forth in claim 1 or 2 and is further characterized in that circular knitted fabric is a single knit and the high shrinkage yarn is inserted in a width direction.

A circular knitted tubular structure according to claim 4 of the present invention has the construction of the circular knitted tubular structure set forth in claim 1 or 2 and is further characterized in that circular knitted fabric is a double knit and the high shrinkage yarn is passed in weave on a wrong side at least in part.

A circular knitted tubular structure according to claim 5 of the present invention has the construction of the circular knitted tubular structure set forth in any one of claims 1 through 4 and is further characterized in that a difference in dry heating shrinkage ratio between yarn forming a right side of circular knitted fabric and the high shrinkage yarn is 3 to 80%.

A circular knitted tubular structure according to claim 6 of the present invention has the construction of the circular knitted tubular structure set forth in any one of claims 1 through 5 and is further characterized in that yarn including monofilament having a single yarn fineness of 30 to 2400 dtex or multi-filament having a single yarn fineness of 30 to 2400 dtex or both is passed on a wrong side of circular knitted fabric.

A circular knitted tubular structure according to claim 7 of the present invention has the construction of the circular knitted tubular structure set forth in any one of claims 1 through 6 and is further characterized in that knit loops forming a right side of circular knitted fabric include loops having at least two loop lengths, and that loops having a shortest loop length account for 20 to 75% of all knit loops per unit area and a loop length of the loops having the shortest loop length is 20 to 80% of a loop length of loops having a longest loop length.

A manufacturing method of a circular knitted tubular structure according to claim 8 of the present invention is characterized by including: knitting front yarn and back yarn having a higher heat shrinkage ratio than the front yarn into circular knitted fabric with a circular knitting machine by forming a front loop from the front yarn and passing the back yarn behind the front loop; producing a fabric tape by cutting the circular knitted fabric knitted in advance in a course direction which is a length direction of knitted fabric at an interval of 1 to 30 cm in a width direction; and forming the fabric tape into a scrolled shape with one end overlapping the other to have a scrolled overlap portion circumferentially overlapping 1.3 to 2.5 times in the scrolled shape by passing the fabric tape through a dried furnace at 70 to 190° C. in a range within which a length of the fabric tape becomes 0.8 to 1.3 times longer than an original length while the fabric tape is passed through a conical shape-forming induction jig which has a circular opening at an inlet and a scrolled, tapered opening at an outlet.

A manufacturing device of a circular knitted tubular structure according to claim 9 of the present invention includes a furnace heating a fabric tape formed of circular knitted fabric and a shape-forming induction jig shaping the fabric tape, and is characterized in that: the shape-forming induction jig is of a conical shape having a circular opening at an inlet and a scrolled, tapered opening at an outlet, and that the shape-forming induction jig shapes the fabric tape inserted into the inlet and pulled out from the outlet into a scrolled shape with one end overlapping the other and allows the fabric tape to remain scrolled by heating in the furnace.

Advantageous Effects of Invention

According to the present invention, a fabric tape cut from circular knitted fabric in the length direction hardly frays from a cut edge of the fabric tape. Hence, a circular knitted tubular structure formed of the fabric tape has an advantage that fray hardly occurs. The tubular structure can be manufactured from a fabric tape cut in a desirable width from circular knitted fabric made by a single circular knitting machine independently of a cylinder diameter and can be therefore manufactured at low costs. The circular knitted fabric itself has stretching properties. Hence, a circular knitted tubular structure formed of the circular knitted fabric is sufficiently pliable and has high adaptability to bending. The fabric tape is allowed to form a tubular structure naturally due to heat shrinkage of high shrinkage yarn having a high heat shrinkage ratio, and an opening can be readily opened because the fabric tape is formed of circular knitted fabric. Also, the tubular structure closes by itself after cables or the like are stored inside due to a shrinking action of the high shrinkage yarn, thereby eliminating a need to purposely close the tubular structure. A circular knitted tubular structure formed of circular knitted fabric has soft tube inner and outer surfaces. Hence, there is an advantage that no abnormal noise is produced not only when a cable stored inside hits against the inner surface of the circular knitted tubular structure due to vibration, but also when the outer surface of the circular knitted tubular structure hits against a nearby structure or the like. Consequently, a highly useful protection sleeve covering and thereby protecting a cable, such as an electrical wire and an optical fiber cable, can be provided.

In the manufacturing method of the present invention, the conical shape-forming induction jig having a circular opening at the inlet and a scrolled, tapered opening at the outlet and the furnace are used. A fabric tape can be formed into a scrolled shape in a reliable manner by the shape-forming induction jig. Also, by passing the fabric tape formed into a scrolled shape through the furnace, a circular knitted tubular structure that remains scrolled in a tubular shape can be manufactured.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic view of a right side of a fabric tape formed of circular knitted fabric and forming a circular knitted tubular structure using a single knit of the present invention;

FIG. 2 is a schematic view of a wrong side of the fabric tape formed of circular knitted fabric and forming a circular knitted tubular structure using the single knit of the present invention;

FIG. 3 is a weave diagram of the single knit shown in FIG. 1 and FIG. 2;

FIG. 4 is a partial perspective view of a circular knitted tubular structure using the single knit of the present invention;

FIG. 5 is a partial perspective view of a circular knitted tubular structure using a double knit of the present invention;

FIG. 6 is a weave diagram of the double knit of the present invention;

FIG. 7 is a partial perspective view of a circular knitted tubular structure having an overlap portion circumferentially overlapping less than 1.3 times;

FIG. 8 is a partial perspective view when the circular knitted tubular structure having the overlap portion circumferentially overlapping less than 1.3 times is curved;

FIG. 9 is a partial perspective view of a circular knitted tubular structure having an overlap portion circumferentially overlapping more than 2.5 times;

FIG. 10 is a partial perspective view of a deformed circular knitted tubular structure as an example of failure in manufacture;

FIG. 11 is a schematic view of a manufacturing device manufacturing a circular knitted tubular structure of the present invention;

FIG. 12 is a front perspective view of a shape-forming induction jig used to manufacture a circular knitted tubular structure of the present invention;

FIG. 13A and FIG. 13B are schematic views of an accelerated wear testing machine, FIG. 13A being a front view and FIG. 13B being a side view;

FIG. 14 is a plan view of an entire rubber film;

FIG. 15 is a partially enlarged front view of the rubber film;

FIG. 16 is a picture showing a difference in fray between Example 1 and Comparative Example 1, (a) in the drawing showing Example 1 and (b) in the drawing showing Comparative Example 1;

FIG. 17 is a picture showing evaluation results of pliability to bending in Example 1 and Comparative Example 1, a row A in the drawing showing Example 1 and a row B in the drawing showing Comparative Example 1; and

FIG. 18 is an enlarged picture showing a difference in change between tubular structures of Comparative Example 1.

DESCRIPTION OF EMBODIMENTS Single Knitted Fabric

A summary of a circular knitted tubular structure of the present invention and a manufacturing method thereof will be described by referring to an example of a manufacturing process of a tubular structure using a single knit. Circular knitted fabric is knitted in a cylindrical shape by a circular knitting machine to hang downward below the circular knitting machine. Hence, a top-bottom direction of the circular knitted fabric coming out from the knitting machine is a course direction (length direction) and a horizontal direction is a wale direction (width direction) of the circular knitted fabric. In the present invention, a fabric tape is produced by cutting and opening circular knitted fabric knitted in advance along stitches in the course direction of the knitted fabric and by cutting the opened knitted fabric in the length direction at appropriate width intervals. A fabric tape 10 formed of single circular knitted fabric is shown in FIG. 1 and FIG. 2, in which a top-bottom direction is the length direction of the fabric tape and a right-left direction is the width direction. FIG. 3 is a weave diagram of circular knitted fabric in single knit forming a circular knitted tubular structure A.

As is shown in FIG. 3, the single circular knitted fabric has front yarn 11 (total fineness of 167 dtex, plain knit of 48 polyethylene terephthalate filament textured yarn) forming knit loops on a right side and back yarn 12 (high shrinkage yarn, 670 dtex, polypropylene monofilament inlay yarn) having a higher heat shrinkage ratio than the front yarn 11. The front yarn 11 is chained in right, left, up and down to form knit loops and the back yarn 12 is inserted through the front yarn 11 forming front loops on the right, left, up and down in a traverse direction (one tuck in every three welts). FIG. 1 shows a right side of the fabric tape 10 formed of circular knitted fabric (right side of circular knitted fabric). FIG. 2 shows a wrong side of the fabric tape 10 formed of circular knitted fabric (wrong side of circular knitted fabric) and the back yarn 12 behind the front yarn 11 is shown partially.

When the fabric tape 10 is heated, the back yarn 12 having a high heat shrinkage ratio undergoes heat shrinkage. Eventually, the fabric tape 10 curves in a direction in which both ends in the width direction come close to each other and becomes deformed into a cylindrical shape with a side where the back yarn 12 is inserted facing inward. FIG. 4 shows a cylindrically deformed state. As is shown in FIG. 4, the fabric tape 10 scrolled with one end overlapping the other forms the circular knitted tubular structure A. After an electrical wire or a cable is inserted into the circular knitted tubular structure A by opening the overlap portion, a self-closing function is exerted due to shrinkage of the back yarn 12 which is heat shrinkage yarn and the opening of the overlap portion naturally closes without having to close the opening of the overlap portion manually.

Double Circular Knitted Fabric

An example of a circular knitted tubular structure using a double knit will now be described. A circular knitted tubular structure 1A of FIG. 5 is a tubular structure formed of circular knitted fabric in double knit. FIG. 6 is a weave diagram of circular knitted fabric in double knit forming the circular knitted tubular structure 1A. In FIG. 6, numeral 111 denotes front yarn forming front loops. That is, the front yarn 111 forms front loops by plain knitting on a cylinder side. Alpha-numerals 112 a and 112 b denote back yarns each forming back loops. The back yarn 112 a is high shrinkage yarn. That is, the back yarn 112 a forms back loops on a dial side by plain knitting and the back yarn 112 b forms back loops on the dial side by plain knitting. Besides the front yarn 111 and the back yarns 112 a and 112 b, circular knitted fabric in double knit has engaging yarn 113 connecting the front yarn 111 to the back yarns 112 a and 112 b by tangling with the front yarn 111 and the back yarns 112 a and 112 b.

The front yarn 11 described in Example 1 below is used as the front yarn 111 and the back yarn 112 b. The back yarn 12 described in Example 1 below is used as the back yarn 112 a. Also, 24 polyethylene terephthalate filament textured yarn having a total fineness of 56 dtex is used as the engaging yarn 113. The circular knitted tubular structure 1A is same as the circular knitted tubular structure A described above except that it is formed of circular knitted fabric in double knit in which the back yarn 112 a and the back yarn 112 b form back loops, and a description is omitted herein.

Yarn Forming Right Side

Composition of circular knitted fabric forming a tubular structure of the present invention will now be described.

Yarn forming a right side of knitted fabric (herein, referred to as front yarn) by forming knit loops on the right side of knitted fabric is not particularly limited and can be any soft yarn capable of conferring covering properties to knitted fabric. A total fineness of the front yarn is preferably 30 to 2400 dtex, and more preferably 100 to 1200 dtex. When a total fineness is lower than 30 dtex, the covering properties readily deteriorate. Conversely, when a total fineness is as high as or higher than 2400 dtex, the tubular structure becomes heavy.

A single yarn fineness of the front yarn is preferably 0.3 to 20 dtex, and more preferably 0.5 to 10 dtex. When a single yarn fineness is lower than 0.3 dtex, fiber readily snags to a hangnail or a protruding object. Conversely, when a single yarn fitness is over 20 dtex, a fiber end coming out from the edge cut and left as is makes an individual feel scratchy by touching skin of the individual, or readily damages a nearby object by rubbing against the nearby object.

A material of the front yarn is not particularly limited, and can be a synthetic fiber, such as polyester, nylon, and acrylic, a natural fiber, such as cotton, linen, and sheep wool, and either recycled or semisynthetic organic fiber represented by rayon, lyocell, cupra, and acetate. Either a filament fiber or a staple fiber can be used. For example, in a case where a filament fiber often used for a cable is used, flat yarn may be used or yarn texturing, such as false twisting, air interlacing, and covering may be applied. Alternatively, both of a staple fiber and a filament fiber may be used as staple-filament conjugate spun yarn formed by using a core spun yarn technique or a fine spinning and twisting method or as covered yarn formed by covering spun yarn with a filament fiber. As a relatively inexpensive and durable example, untextured yarn or false twisted textured yarn of polyester multi-filament is used preferably.

High Shrinkage Yarn (Back Yarn)

It is preferable to use yarn having a higher heat shrinkage ratio (hereinafter, referred to as high shrinkage yarn) than yarn forming the right side at least in part of the wrong side of the knitted fabric of the present invention. The high shrinkage yarn is preferably yarn which shrinks 3 to 80% better than the front yarn when differential shrinkage between the front yarn and the high shrinkage yarn on the wrong side is checked in a dry heating shrinkage test conducted at 150° C. as will be described below. The differential shrinkage may be selected as needed according to a diameter of a desirable tubular structure. It is preferable to set relatively large differential shrinkage of 25 to 80% for a tubular structure having a relatively small diameter of 2 to 20 mm while it is preferable to set relatively small differential shrinkage for a tubular structure having a diameter larger than 20 mm.

Large Size Yarn

In the present invention, it is preferable to use large size yarn to confer a shape retaining property and an elastic bouncing property to the tubular structure. Large size yarn includes at least filaments having single yarn fineness of 30 to 2400 dtex, and more preferably 300 to 1200 dtex. Large size yarn includes one to five filaments, more preferably, one filament each having the single yarn fineness specified above. However, it goes without saying that large size yarn may be a monofilament alone. Large size yarn may be used on the right side or the wrong side or both.

It is most preferable to use high shrinkage, large size yarn as yarn on the wrong side. In a case where high shrinkage, large size yarn is on the wrong side, a cut end of large size yarn shrinks and sinks into the knitted fabric from the end of the knitted fabric when the tubular structure is shaped by heating. Hence, there is an advantage that the end of large size yarn hardly makes contact with an outside.

Material of Back Yarn

A material of yarn on the wrong side (back yarn) is not particularly limited and a synthetic fiber filament is used preferably. For example, a polyester fiber chiefly made of polyethylene terephthalate, polybutylene terephthalate, or polytrimethylene terephthalate, a polyamide fiber, such as nylon 6 and nylon 66, a polyolefin fiber, such as polyethylene and polypropylene, a polyparaphenylene benzoxazole fiber, an aramid fiber, and a polyarylate fiber can be used.

These fibers may be conjugated into blended filament yarn, twisted union yarn, or conjugated yarn. Alternatively, either flat yarn or textured yarn, such as false twisted textured yarn, may be used. In a case where high shrinkage, large size yarn is used as the back yarn of the present invention, a polypropylene fiber or a polyester fiber can be used preferably.

Material Ratio

It is preferable that high shrinkage back yarn accounts for 10 to 80 wt % on the basis of the entire circular knitted fabric. When high shrinkage yarn accounts for the range specified above, a cylindrical shape having a neatly scrolled, overlap portion can be easily formed. A more preferable range is 25 to 60 wt %, and further preferable range is 30 to 60 wt %. When the high shrinkage yarn accounts for less than 10 wt %, a shape retaining property and an elastic bouncing property of the tubular structure deteriorate and a cable protecting effect cannot be fully exerted. Conversely, when the high shrinkage yarn accounts for more than 80 wt %, high shrinkage back yarn becomes too thick and readily snags.

Preferably Used Construction of Knitted Fabric

Knitted fabric used for the tubular structure of the present invention is knitted fabric formed by knitting yarn while forming knit loops one by one in the traverse direction. Examples of such knitted fabric include but not limited to circular knitted fabric and weft knitted fabric. Weft knitted fabric is advantageous over circular knitted fabric because there is no need to open the fabric whereas circular knitted fabric is advantageous over weft knitted fabric in terms of productivity.

Circular knitted fabric is largely divided to single circular knitted fabric and double circular knitted fabric and both can be used suitably in the present invention. Single circular knitted fabric is advantageous over double circular knitted fabric when a thin and narrow tubular structure is desirable whereas it is preferable to use double circular knitted fabric when a thick and highly-elastic tubular structure is desirable.

Thickness and Mass Per Unit Area of Knitted Fabric (Gray Fabric)

In a case where single circular knitted fabric is used as the knitted fabric of the present invention, a thickness of the knitted fabric is preferably 0.3 to 1.0 mm. When the thickness is less than 0.3 mm, a shape retaining property of the tubular structure readily deteriorates. Conversely, when the thickness is over 1.0 mm, the tubular structure becomes hard to twist when attached to a cable or the like and workability readily deteriorates. A mass per unit area of single circular knitted fabric is preferably 70 to 230 g/m². When the mass per unit area is less than 70 g/m², a shape retaining property readily deteriorates. Conversely, when the mass per unit area is over 230 g/m², the tubular structure becomes heavy, which may become a disadvantage in a field where a lighter weight is required, for example, for vehicular use.

In a case where double circular knitted fabric is used as the knitted fabric of the present invention, a thickness of the knitted fabric is preferably 0.5 to 1.5 mm. When the thickness is less than 0.5 mm, a shape retaining property of the tubular structure readily deteriorates. Conversely, when the thickness is over 1.5 mm, the tubular structure becomes hard to twist when attached to a cable or the like and workability readily deteriorates. A mass per unit area of double circular knitted fabric is preferably 100 to 370 g/m². When the mass per unit area is less than 100 g/m², a shape retaining property readily deteriorates. Conversely, when the mass per unit area is over 370 g/m², the tubular structure becomes heavy, which may become a disadvantage in a field where a lighter weight is required, for example, for vehicular use.

Overlap

In the present embodiment, the circular knitted tubular structure A is formed by shaping the fabric tape 10 into a scrolled shape with one end overlapping the other to have an overlap portion circumferentially overlapping 1.3 to 2.5 times. FIG. 7 shows a circular knitted tubular structure B with an overlap portion circumferentially overlapping less than 1.3 times, which is not suitable because, as is shown in FIG. 8, when the circular knitted tubular structure B enclosing electrical wires, cables, or the like is curved, the overlap portion opens and the electrical wires, the cables, or the like enclosed inside become exposed from the circular knitted tubular structure B. FIG. 9 shows a circular knitted tubular structure C with an overlap portion circumferentially overlapping more than 2.5 times, which is not suitable, either, because it becomes difficult to insert electrical wires, cables, or the like into an internal space of the circular knitted tubular structure C.

Diameter and Mass Per Unit Area of Tubular Structure

A tubular structure formed of circular knitted fabric of the present invention is applicable with a diameter of 2 to 50 mm. When the diameter is less than 2 mm, it becomes difficult to form a scrolled tubular structure. Conversely, when the diameter is over 50 mm, a shape retaining property readily deteriorates because cables filled inside becomes larger and heavier as the diameter becomes larger, in which case a protecting effect high enough for heavy cables cannot be obtained.

A preferable mass per 1 m in consideration of a diameter of the tubular structure is indicated by a mass per unit area (g/m)/diameter (mm). In the case of single circular knitted fabric, a value of the mass per unit area diameter is preferably set to 0.6 to 1.5. In the case of double circular knitted fabric, the value is preferably set to 1.2 to 3.0. When the value is less than the lower limits in the respective ranges specified above, a shape retaining property of the tubular structure readily deteriorates. Conversely, when the value is over the upper limits, the tubular structure may become too heavy.

Fabric Tape

A fabric tape of the present invention can be produced by cutting circular knitted fabric in the length direction at intervals of 1 to 50 cm in the width direction. A preferable width of the fabric tape is 2 to 30 cm. It becomes difficult to form a neat cylindrical tubular structure from a fabric tape having a width of less than 1 cm. Conversely, a tubular structure formed of a fabric tape having a width of 50 cm or wider is likely to have poor shape retaining property. Circular knitted fabric can be cut in the length direction by any cutting method unless a cut surface becomes hard or readily snags. For example, circular knitted fabric can be cut by using an edged tool, such as scissors and a knife, an ultrasonic wave, an airflow, a water flow, and so on. A side surface of the fabric tape of the present invention cut by any of the methods specified above is used intact as a selvage. The manufacturing process of the tubular structure can be thus simpler, and hence the tubular structure can be manufactured efficiently at lower costs. In the present invention, a state of fabric cut and left without any fray-proof treatment is referred to as “cut and left as is”.

It is also preferable to form a shape of the opened circular knitted fabric before it is cut into tapes by applying primary heat treatment at a low temperature, for example, lower than 150° C. to allow the opened circular knitted fabric to stay in a flat state without becoming curled under no load. The low-temperature heat treatment is to improve workability in the following step of cutting the opened circular knitted fabric into fabric tapes and is not essential. However, the low-temperature heat treatment is useful particularly for single circular knitted fabric. That is, circular knitted fabric readily becomes curled or skewed when opened. Hence, the opened circular knitted fabric straightened in a flat state by the low-temperature heat treatment has an advantage that it becomes easier to produce fabric tapes because the circular knitted fabric can be cut readily and neatly.

Shape-Forming Method

The knitted fabric of the present invention cut into a fabric tape can be formed into a scrolled tubular structure by heating due to differential shrinkage between the right side and the wrong side. Any heating method available to heat fibers can be used and examples include but not limited to dry heating using a convection of heated air by a hot-air drying machine or the like, wet heating using a steamer or the like, contact heating with hot metal or heat medium, wet infra-red radiation, and electromagnetic heating using a microwave or the like. Alternatively, two or more of these methods may be used in combination. A method using a hot-air drying machine or contact heating is preferable.

For example, when a hot-air drying machine is used, an operating temperature of the drying machine may be set to 50 to 210° C., and more preferably 70 to 190° C. A fabric tape can be made long in the length direction. Hence, a device including heating equipment provided with an inlet and an outlet and capable of treating a fabric tape continuously is used preferably in terms of improvement of productivity.

A fabric tape also shrinks in width by heating. That is, a width of a fabric tape once formed into a scrolled tubular structure by heating and developed into a flat state is less than a width of the fabric tape before heating due to shrinkage and the latter is reduced to approximately two thirds of the former.

Scrolled Shape-Forming Induction

As has been described, the knitted fabric of the present invention cut into a fabric tape can be formed into a scrolled tubular structure by heating due to differential shrinkage between the right side and the wrong side. However, while the circular knitted tubular structure A is being manufactured, as is shown in FIG. 10, both ends of a fabric tape in the width direction may come close to each other and curve inward while pressing against each other. Consequently, a double-crest circular knitted tubular structure A′ is formed. In this case, the fabric tape may be formed into a scrolled shape by placing one end on the other. However, a curving force may be weaker than is expected, in which case the self-closing function may become poor or an overlap portion may be formed insufficiently. In view of the foregoing, it is preferable for a manufacturing method of the present invention to forcedly scroll the circular knitted fabric by using a conical shape-forming induction jig having a circular opening at an inlet and a scrolled, tapered opening at an outlet as will be described below.

FIG. 11 is a schematic view showing an example of a manufacturing device of a circular knitted tubular structure. A manufacturing device D of a circular knitted tubular structure includes a furnace 30 heating the fabric tape 10 formed of circular knitted fabric, and a shape-forming induction jig 20 provided inside the furnace 30 and forming a shape of the fabric tape 10 into a scrolled shape. The shape of the fabric tape 10 is formed into a scrolled shape with one end overlapping the other by the shape-forming induction jig 20. As the fabric tape 10 is heated in the furnace 30 while passing through the shape-forming induction jig 20, high shrinkage back yarn in the fabric tape 10 undergoes heat shrinkage and the circular knitted tubular structure A formed into a scrolled shape remains scrolled. The circular knitted tubular structures A and 1A each remaining scrolled as are shown, respectively, in FIG. 4 and FIG. 5 are thus completed.

As is shown in FIG. 12, the shape-forming induction jig 20 is formed by scrolling a flat plate into a conical shape. An opening at the inlet where the fabric tape 10 is inserted is provided as a large circular opening 21 because the fabric tape 10 is in a flat state. An opening at the outlet is a scrolled, tapered opening 22 because the fabric tape 10 is deformed into a scrolled shape. By inserting the fabric tape 10 from the opening 21 at the inlet of the shape-forming induction jig 20 for the right side to form a scrolled inner peripheral surface while pinching part of the fabric tape 10 in a scrolled overlap portion of the opening 21 and pulling out the fabric tape 10 from the tapered scrolled opening 22 at the outlet, a shape of the flat fabric tape 10 is forcedly formed into a scrolled shape with one end overlapping the other. A circular shape of the opening 21 at the inlet is not limited to a shape of a true circle and also includes a shape of an ellipse.

Shape-Forming Condition

The following will describe an example of concrete shape-forming conditions using the manufacturing device. By heating the fabric tape 10 at 70 to 190° C. in a range within which the fabric tape 10 becomes 0.8 to 1.3 times as long as the original length in the length direction while the fabric tape 10 is passed through the shape-forming induction jig 20 shown in FIG. 12 to let the heat shrinkage yarn undergo heat shrinkage, the fabric tape 10 is curved into a scrolled shape with one end overlapping the other. The circular knitted tubular structure A with the overlap portion circumferentially overlapping 1.3 to 2.5 times is thus manufactured. Herein, a range within which the fabric tape 10 becomes 0.8 to 1.3 times longer than the original length of the fabric tape 10 means a range from a numerical value of the fabric tape 10 that is shrunken when pushed into the shape-forming induction jig 20 to a numerical value of the fabric tape 10 that is stretched when pulled out from the shape-forming induction jig 20 while the fabric tape 10 is passed through the shape-forming induction jig 20.

EXAMPLES

The following will describe the present invention concretely by way of examples and a comparative example. It should be appreciated, however, that the present invention is not limited to the examples below. Respective physical values used in the present invention are measured as follows.

Total Fineness of Yarn (dtex)

A total fineness of yarn is measured by a fineness based on corrected mass in accordance with JIS L1013 8.3.1.

The Number of Filaments

The number of filaments is measured by the number of filaments in accordance with JIS L1013 8.5.1.

Single Yarn Fineness (dtex)

A fineness of monofilament (single yarn fineness) in yarn is found from a total fineness and the number of filaments measured as above.

single yarn fineness (dtex)=total fineness/the number of filaments

Dry Heating Shrinkage Ratio (%) of Yarn

A length of a sample, L1 (mm), under a load of 1/27 g/dtex is measured. Subsequently, the load is removed and the sample is placed in a drying machine and dried for 30 minutes at 160° C. The dried sample is allowed to cool to room temperature and a length L2 (mm) is measured again under a load of 1/30 g/dtex. A dry heating shrinkage ratio at 160° C. is calculated by substituting L1 and L2 into an equation as below. A measured value used herein is an average value found by performing the measurement five times.

dry heating shrinkage ratio(%)=[(L1−L2)/L1]×100

Density of Knitted Fabric (Stiches/2.54 cm)

Density of knitted fabric is measured by density of knitted fabric in accordance with JIS L1096 8.6.2.

Thickness

A thickness is measured by a thickness measured by the method in accordance with JIS L1096 8.4B.

Mass Per Unit Area of Knitted Fabric (g/m²) and Mass Per Unit Area of Tubular Structure (g/m)

A mass per unit area of knitted fabric is measured by a mass per unit area measured by the method in accordance with JIS L1096 8.3B. A mass of a tubular structure per meter is measured and a mass per unit length is used as a mass per unit area of the tubular structure.

Ease of Fray from Cut Edge of Tubular Structure

Ease of fray from a cut edge (lateral side of the tubular structure) in the length direction of the tubular structure is measured by the method in accordance with JIS L1096 8.19.4D (measurement in acceleration) which is a wear resistance measuring method. A tubular structure is cut into a 10-cm-long piece in the length direction. An entire edge of the cut piece except for 5 mm from the cut edge in the length direction is fixed by bonding so as not to fray during a test. No adhesive is applied to the cut edge (lateral side of the tubular structure) where ease of fray is measured. The cut piece is ironed at a temperature low enough not to melt a fiber material forming the tubular structure to flatten the tubular structure of a scrolled shape. A measuring sample is thus prepared.

FIGS. 13A and 13B show an accelerated wear testing machine E used to confirm ease of fray. In FIGS. 13A and 13B, a letter a denotes a metal rotary blade, a letter b denotes a cylinder, a letter c denotes a rubber film, a letter d denotes a glass plate, and a letter e denotes a lid. Normally, abrasive paper is laminated on an inner peripheral surface of the cylinder b forming the testing machine E. However, the rubber film c with projections and depressions as are shown in FIGS. 15 and 16 is used instead of abrasive paper in this testing machine. The rubber film c is formed of a rubber material having a length of 43.5 cm which is same as an inner peripheral length of the cylinder b, a depth of 7.0 cm which is same as a depth of the cylinder, a thickness of 0.35 cm (a gap h between the projections and the depressions is 0.2 cm), a rubber hardness of 82 to 83A, and a mass of 125 g±1 g. In the testing machine E, the measuring sample is pinched under the rotary blade a and the measuring sample is rotated in suspension within the cylinder by rotating the rotary blade a for two minutes at a rotation speed of 2000 revolutions per minute. Subsequently, the measuring sample is removed from the cylinder and the number of strands of yarn frayed from the cut edge in the length direction is counted. A strand frayed by half the length or more of the cut edge of the measuring sample is counted as a frayed strand. The measuring sample is evaluated as a failure unless there is no frayed stand.

Bendability of Tubular Structure

Bendability of the tubular structure is evaluated by forming a tubular structure into a ring by connecting both ends in circle and checking whether an angular bent portion is created on the inner periphery. A tubular structure formed into a smaller circle and creating no bent portion has more excellent bendability.

(1) An evaluation tubular structure is cut in a length of a desired inner peripheral length plus an allowance of 10 mm.

Evaluation rings having six different diameters (mm) (circumferential lengths (mm)) as follows are prepared. Diameters and circumferential lengths are based on inner diameters of the rings.

Diameters (circumferential lengths): 100 (314), 75 (236), 50(53) 30 (94), 15 (47), and 10(31).

(2) A method of preparing a sample will now be described in detail. For example, in a case where a ring having an inner diameter of 100 mm is formed, the tubular structure is cut into a length of 314 mm plus an allowance of 10 mm=324 mm. The allowance is overlapped on a circle having the inner diameter to prevent the circle from being deformed in the allowance. The allowance is stitched together at a center of the tubular structure along the circumference by a sewing machine by lock stitch at a pitch of 1 mm. An evaluation sample is thus prepared.

(3) The evaluation sample allowed to stand on a horizontal desk is viewed from directly above and evaluated according to criteria as follows.

According to the following evaluation criteria, an evaluation sample ranked at 5 to 3 passes the test and an evaluation sample ranked at 2 or 1 fails the test.

5: the shape is substantially perfect circular shape and no wrinkle and crease are confirmed.

4: the shape is a substantially perfect circular shape and a wrinkle is confirmed at one or more than one point on the inner peripheral surface of the circle

3: a large number of wrinkles are confirmed on the inner peripheral surface of the circle

2: the shape is an imperfect circular shape and creases are confirmed at several points on the inner peripheral surface

1: a large number of angular v-shaped creases are generated and hence the shape is deformed into a polygonal shape

Example 1

A single circular knitting machine available from Precision Fukuhara Works, Ltd. (VX-JS3, diameter: 30 inches, and gauge: 22G) is used. Front yarn used is double-heater false twisted textured yarn (dry heating shrinkage ratio: 3%) of 48 polyethylene terephthalate filament at 167 dtex. Insertion yarn used on the wrong side is polypropylene monofilament at 670 dtex having a dry heating shrinkage ratio of 30% (large size, high shrinkage yarn). Fabric is knitted by inserting one strand of insertion yarn into two stands of front yarn according to a ratio of a structure in the weave diagram of FIG. 3. Density of the resulting knitted fabric is 50 stitches/2.54 cm in the course direction and 44 stiches/2.54 cm in the wale direction. A thickness and a mass per unit area of the knitted fabric are 0.60 mm and 140 g/m², respectively. As to a material mixing ratio, polyethylene terephthalate accounts for 67% and polypropylene accounts for 33%.

The knitted fabric is opened and cut like a slit in the length direction by using scissors. An 8-cm-wide fabric tape is thus produced. By subjecting the fabric tape to heat shape-forming processing for two minutes at a preset temperature of 170° C. in the hot-air drying machine by using the shape-forming induction jig described above, a width of the fabric tape is reduced by shrinkage and the insertion yarn on the wrong side shrinks. A tubular structure having a diameter of 1 cm and an overlap portion circumferentially overlapping 1.7 times is thus manufactured.

Example 2

A double circular knitting machine available from Precision Fukuhara Works, Ltd. (V-LPJ4, diameter: 30 inches, and gauge: 20G) is used. Front yarn used on the cylinder side of the knitting machine is false twisted textured yarn of 48 filament at 167 dtex and having a dry heating shrinkage ratio of 3%, that is, yarn same as the front yarn used in Example 1 above. Back yarn used on the dial side of the knitting machine is polypropylene monofilament at 220 dtex having a dry heating shrinkage ratio of 30% and false twisted textured yarn at 167 dtex same as the front yarn. Fabric is knitted by interlock knitting according to the weave diagram of FIG. 6 by changing the back yarns alternately. Density of the resulting knitted fabric is 48 stitches/inch in the course direction and 26 stitches/inch in the wale direction. A thickness and a mass per unit area of the knitted fabric are 1.2 mm and 250 g/m², respectively. The knitted fabric is cut in the same manner as in Example 1 above and an 8-cm wide fabric tape is produced. In the fabric tape, polyethylene terephthalate accounts for 70% and polypropylene accounts for 30%.

By subjecting the fabric tape to heat shape-forming processing for two minutes at a preset temperature of 170° C. in the hot-air drying machine by using the shape-forming induction jig described above, a width of the fabric tape is reduced by shrinkage and the back yarns on the wrong side shrink. A tubular structure having a diameter of 1 cm and an overlap portion circumferentially overlapping 1.7 times is thus manufactured.

Comparative Example 1

The following will describe a tubular structure formed of woven fabric by way of example as Comparative Example 1.

A warp used is mono-heater false twisted textured yarn (black spun-dyed yarn having a dry heating shrinkage ratio of 3%) formed by warping fiber of 48 polyethylene terephthalate filament at 167 dtex. A weft used is polypropylene monofilament (black spun-dyed yarn) at 660 dtex having a dry heating shrinkage ratio of 30%. By weaving the warp and the weft with a rapier loom available from Ishikawa Seisakusho, LTD, woven fabric of 3/1 right twill weave having density in gray fabric of 38 warp strands/2.5 cm and 25 weft strands/2.5 cm and a woven width of 100 cm is manufactured. The woven fabric is cut with heat along a warp by using flat soldering iron and a ruler. An 8-cm-wide fabric tape with the both side surfaces made fray-proof by heat cutting is thus manufactured.

The fabric tape is heated by using the shape-forming induction jig described above by same operations under same processing conditions and formed into a tubular structure. The tubular structure thus obtained has a diameter of 1 cm and an overlap portion circumferentially overlapping 1.7 times.

The single circular knitted fabric (Example 1) and the double circular knitted fabric (Example 2) formed as above have stretching properties in circular knitted fabric in itself. Hence, the tubular structure formed of the circular knitted fabric is sufficiently pliable and has extremely excellent adaptability to bending in comparison with a tubular structure formed of woven fabric. As is shown in FIG. 16, a side cut portion of the tubular structure of Example 1 ((a) in the drawing) does not fray at all in the wear test according to “ease of fray in the cut edge of the tubular structure” described above. On the contrary, an end face of the woven fabric cut with heat in Comparative Example 1 ((b) in the drawing) is hard and snags to a hand. As is shown in FIG. 16, fray occurs markedly in the wear test.

Pliability to bending is evaluated in each of the tubular structures of Example 1 and Comparative Example 1. Evaluation results are set forth in Table 1 below and shown in FIG. 17 and FIG. 18. Of circular shape evaluation samples in Comparative Example, samples having inner diameters of 15 mm and 10 mm are not evaluated because a sample having an inner diameter of 30 mm already appears angular.

TABLE 1 Tube diameter Inner diameter value (mm) of circle (mm) 200 150 100 75 50 30 15 10 Example 1 10 5 5 5 5 5 5 4 4 Comparative 10 5 5 4 3 2 1 1 1 Example 1

FIG. 17 is a picture showing a change in shape in Example 1 when an inner diameter is changed in six steps as in a row A: 100 mm (A1 in the drawing), 75 mm (A2 in the drawing), 50 mm (A3 in the drawing), 30 mm (A4 in the drawing), 15 mm (A5 in the drawing), and 10 mm (A6 in the drawing), and a change in shape in Comparative Example 1 when an inner diameter is changed in four steps as in a row B: 100 mm (B1 in the drawing), 75 mm (B2 in the drawing), 50 mm (B3 in the drawing), and 30 mm (B4 in the drawing). FIG. 18 is an enlarged picture of the samples having inner diameters of 75 mm and 50 mm of Comparative Example 1 shown in FIG. 17, which shows that tubular structures change markedly. In Comparative Example 1, many wrinkles are confirmed on the inner peripheral surface of the circle in the sample having an inner diameter of 75 mm (B2 in the drawing) as are indicated by arrows, and wrinkles and creases are confirmed at several points on the inner peripheral surface of the circle of the sample having an inner diameter of 50 mm (B3 in the drawing) as are indicated by arrows and a circular shape is deformed.

REFERENCE SIGNS LIST

-   A: circular knitted tubular structure formed of single circular     knitted fabric -   10: fabric tape -   11: front yarn forming front loops -   12: back yarn having high heat shrinkage ratio -   B: circular knitted tubular structure of Comparative Example 1 -   C: circular knitted tubular structure of Comparative Example 2 -   1A: circular knitted tubular structure formed of double circular     knitted fabric -   111: front yarn forming front loops -   112 a: back yarn forming back loops and having high heat shrinkage     ratio -   112 b: back yarn forming back loops -   113: engaging yarn -   A′: double-crest circular knitted tubular structure -   20: shape-forming induction jig -   21: flat opening -   22: scrolled opening -   D: manufacturing device of circular knitted tubular structure -   30: furnace -   E: accelerated wear testing machine -   a: metal rotary blade -   b: cylinder -   c: rubber film -   d: glass plate -   e: lid 

1. A circular knitted tubular structure formed of a circular knitted fabric tape having a length direction as a course direction, wherein: the circular knitted fabric tape has a cut edge in the length direction cut and left as is and is formed into a scrolled tubular shape to have an overlap portion in a width direction.
 2. The circular knitted tubular structure according to claim 1, wherein: the circular knitted fabric tape is formed of circular knitted fabric using yarn forming a right side and high shrinkage yarn passed on a wrong side and having a higher heat shrinkable property than the yarn forming the right side; and the overlap portion of the circular knitted fabric tape circumferentially overlaps 1.3 to 2.5 times in a scrolled shape.
 3. The circular knitted tubular structure according to claim 2, wherein: circular knitted fabric is a single knit and the high shrinkage yarn is inserted in the width direction.
 4. The circular knitted tubular structure according to claim 2, wherein: the circular knitted fabric is a double knit and the high shrinkage yarn is passed in weave on the wrong side at least in part.
 5. The circular knitted tubular structure according to claim 2, wherein; a difference in dry heating shrinkage ratio between the yarn forming the right side of the circular knitted fabric and the high shrinkage yarn is 3 to 80%.
 6. The circular knitted tubular structure according to claim 2, wherein: the yarn passed on the wrong side of the circular knitted fabric includes at least one of monifilament having a single yarn fineness of 30 to 2400 dtex or multi-filament having a single yarn fineness of 30 to 2400 dtex.
 7. The circular knitted tubular structure according to claim 2, wherein; knit loops forming the right side of circular knitted fabric include loops having at least two loop lengths; and loops having a shortest loop length account for 20 to 75% of all knit loops per unit area and a loop length of the loops having the shortest loop length is 20 to 80% of a loop length of loops having a longest loop length.
 8. A manufacturing method of a circular knitted tubular structure, comprising: knitting front yarn and back yarn having a higher heat shrinkage ratio than the front yarn into circular knitted fabric with a circular knitting machine by forming a front loop from the front yarn and passing the back yarn behind the front loop; producing a fabric tape by cutting the circular knitted fabric knitted in advance in a course direction which is a length direction of knitted fabric at an interval of 1 to 30 cm in a width direction; and forming the fabric tape into a scrolled shape with one end overlapping the other to have a scrolled overlap portion circumferentially overlapping 1.3 to 2.5 times in the scrolled shape by passing the fabric tape through a dried furnace at 70 to 190° C. in a range within which a length of the fabric tape becomes 0.8 to 1.3 times longer than an original length while the fabric tape is passed through a conical shape-forming induction jig which has a circular opening at an inlet and a scrolled, tapered opening at an outlet.
 9. A manufacturing device of a circular knitted tubular structure, comprising: a furnace heating a fabric tape formed of circular knitted fabric; and a shape-forming induction jig shaping the fabric tape, the manufacturing device being characterized in that: the shape-forming induction jig is of a conical shape having a circular opening at an inlet and a scrolled, tapered opening at an outlet; and the shape-forming induction jig shapes the fabric tape inserted into the inlet and pulled out from the outlet into a scrolled shape with one end overlapping the other and allows the fabric tape to remain scrolled by heating in the furnace. 